back out the previous check point change. it wasn't necessary.

git-svn-id: svn://bind10.isc.org/svn/bind10/trunk@1067 e5f2f494-b856-4b98-b285-d166d9295462

src/lib/dns/cpp/rdata/generic/ds_43.cc

@@ -71,8 +71,7 @@ DS::DS(const string& ds_str) :
     }
 
     vector<uint8_t> digest;
-    string digest_string = digestbuf.str();
-    decodeHex(digest_string, digest);
+    decodeHex(digestbuf.str(), digest);
 
     impl_ = new DSImpl(tag, algorithm, digest_type, digest);
 }